JPS6058243B2 - Method for producing graft polymer material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Polymeric materials have found wide use in the manufacture of a myriad of products.

There is a constant need for polymeric materials with new properties, or with older properties but at lower cost. The present invention relates to a method for providing new ethylene-based polymeric materials through the use of grafting reactions. The present invention more particularly provides that the reaction is carried out in a reaction tube with internal baffles, under conditions that prevent undue degradation of the initial ethylene polymeric backbone structure, and in the absence of a free radical initiator. , relates to a polymer grafting reaction carried out by a bulk polymerization method. Grafting reactions are generally well known.

A method for the grafting reaction of alpha olefins using derivatives of unsaturated carboxylic acid anhydrides has been described by Natsuta (N
U.S. Pat. This patent describes a grafting reaction carried out in a roll mill or in solution, always in the presence of a free radical initiator. Steinkem
U.S. Pat. No. 3,862,265, issued January 21, 197 in response to the application of p) et al., discloses a grafting reaction process in a screw feed extruder.

The method includes treating the polymeric material in an extruder to cause its degradation prior to introduction of the graft material. The materials are mixed and moved throughout by the action of a screw feed, and the reaction is carried out in the presence of a free radical initiator. U.S. Pat. No. 3, issued March 25, 197, in response to Wu et al.
No. 873,643 describes polymeric materials with grafted cyclic or polycyclic acids and anhydrides.

The backbone polymer is a polyolefin and the grafting reaction is carried out in a heated extruder or roll mill. C
U.S. Pat. No. 3,884,885 issued May 20, 1975 for application describe the preparation of adducts of maleic anhydride grafted onto polyolefin backbone polymers.

The grafting reaction is carried out in an extruder or roll mill at a temperature of 225-350°C. Traditionally used methods for modifying polymeric materials by grafting reactions often result in moderate degradation of the backbone polymer during the reaction or in the presence of graft monomers in the grafted polymeric material product. In many cases, the reaction conditions were such that crosslinking occurred.

Previously used methods often produce large amounts of grafted polymer materials due to uneven heating or incomplete mixing of the reaction components, or heating and cooling cycles that take too long for optimal grafted polymer materials. A molecular weight cloth was generated. Previously used methods often showed low conversion of graft monomer to graft polymer material. It is an object of the present invention to provide a process for the production of ethylene-based graft polymer materials in which crosslinking and undesired degradation of the polymer are present only to a low degree.

It is further an object of the present invention to mix the grafting reaction components and uniformly and rapidly heat the mixture to the grafting temperature. The object of the present invention is to provide such a method. Another object of the present invention is the rapid and substantially complete dispersion of the reactants contained:
A rapid and uniform temperature change of the contained material in the direction parallel to the axis of material flow in the reactor: and a slight temperature gradient in the direction perpendicular to the axis of material flow in the reactor; An object of the present invention is to provide a method for producing an ethylene-based graft polymer material using a tubular reactor having a rainbow-shaped plate.

The ethylene-based graft reaction involves an ethylene-based backbone polymer and a graft monomer to provide the graft polymer material.

The grafting reaction is carried out without the addition of free radical generating additives.
The temperature of the reaction is as low as can be used to keep short reaction times and as high as permitted to avoid excessive decomposition of the backbone polymer. The use of a tubular reactor with an internal baffle plate, with high mixing efficiency and concomitant uniformity of temperature across the contained materials, without fear of the presence of hot spots in the grafting reaction medium. , allowing the use of grafting reaction times at relatively high temperatures. Such hot spots and non-uniform radial temperature distribution in the graft reactor result in degradation of the backbone polymer and otherwise unacceptable or undesirable graft polymer materials. If the residence time of the contained materials can be kept essentially constant and if the temperature gradient perpendicular to the axis of flow can be kept very low, then short periods at high temperatures rather than long periods at low temperatures can be used. I found it advantageous to do it on time. Desirable polymeric materials for use as ethylene-based polymers in the practice of this invention include thermoplastic and elastomeric compounds of ethylene that are capable of accepting grafts.

Suitable thermoplastic and elastomeric compounds of ethylene are polymers of ethylene and copolymers derived from ethylene and C3-C8 alpha olefins, especially C3-C5 alpha olefins. Desirable ethylene-based backbone polymers can generally be divided into two classes. The first is
Backbone polymers that are substantially saturated and include polymers of ethylene and copolymers derived from ethylene and alpha olefins. The second is a backbone polymer comprising a copolymer derived from ethylene and an alpha olefin having a substantially saturated backbone chain and unsaturated side chains. The term alpha olefin includes monoolefins and diolefins, but does not include ethylene. The first class of backbone polymeric materials exhibits significant differences from the second class of materials in the requirements for grafting reactions.

The first class of saturated backbone polymers is subjected to thermal racking to achieve grafting. Grafting reactions occur with thermal racking, but by use of the present invention, excessive backbone polymer degradation can be kept to a low level. Examples of backbone polymers in this class are high-density and low-density polyethylene and copolymers derived from ethylene and at least one of the following monomers: propylene; methyl and ethyl acrylate; methacrylic acid Methyl; acrylic acid and methacrylic acid; carbon monoxide;
Such. A backbone polymer having a substantially saturated backbone chain and unsaturated side chains undergoes grafting reactions primarily at the unsaturation points of the side chains.

Although the presence of even small amounts of unsaturation in the stem chain may participate in the grafting reaction, it does not appear to be a significant factor in the grafting reaction. Grafting on side chains occurs at somewhat lower temperatures than grafting by thermal or racking, and therefore, if appropriate control over the reaction conditions is carried out, less thermal decomposition or decomposition of the backbone can occur. Can be done without grafting onto the coalescence. The uniform residence time, temperature control, and low radial temperature gradient of the present invention make this process associated with a low degree of thermal degradation.

This makes it ideally suited for grafting onto unsaturated side chains. Examples of backbone polymers as materials of the second class are, for example, copolymers of ethylene and diene. Other examples of backbone polymers belonging to this second class include ethylene, or ethylene and other olefins, such as propylene: linear aliphatic nonconjugated dienes having at least 6 carbon atoms, such as 1,4-hexadiene, etc. Includes copolymers with other dienes, conjugated or nonconjugated, such as norbornadiene, dicyclopentadiene, ethylidene, norbornene, and butadiene. Specific examples of such backbone polymers are ethylene, propylene,
It is a copolymer consisting of 1,4-hexadiene and norbornadiene. Grafting monomers suitable for use in the practice of the present invention include unsaturated carboxylic acid anhydrides that are thermally stable at the temperature of the grafting reaction.

Examples of suitable grafting monomers are: methacrylic acid; acrylic acid; glycidyl methacrylate; 2-
Hydroxyethyl acrylate; 2-hydroxymethyl methacrylate; diethyl maleate; monoethyl maleate; di-n-butyl maleate; maleic anhydride;
Maleic acid; Fumaric acid; Itaconic acid; Dodecenyl succinic anhydride; 5-norbornene-2,3-monoanhydride: Nadic anhydride (3,6-endomethylene anhydride
-tetrahydrophthalic acid) etc. In any graft reaction of the present invention, more than one type of backbone polymer can be used in combination as the backbone polymer, and more than one type of graft monomer can be used in combination as the graft monomer. I can do it. The key factors for effectively accomplishing the grafting reaction are tight overall control of the temperature of the reacting materials and maintenance of short and uniform residence times of the materials in the reactor.

If large temperature differences exist within the reaction melt, there is a contradictory degree of reaction, ie, incomplete grafting in the cold zone and decomposition of the polymer in the hot zone. In tubular or extruder reactors, the temperature difference perpendicular (radial) to the overall material flow must be kept to a minimum. In order to keep such temperature differences to a minimum, there must be an efficient radial distribution of the material so that heat transfer occurs radially from one location to another in the reactor. There must be. Axial temperature control is also important to prevent conflicting reaction degrees that can occur due to different exposures to appropriate reaction temperatures. Steady state operation is necessary to conduct an acceptable continuous grafting reaction process. In order to obtain a graft mass of uniform quality, it is important to subject all of the reacting materials to substantially the same reaction temperature for substantially the same amount of time. The reactor exhibiting the necessary temperature control, efficiency of heat transfer, and uniformity of residence time is a tubular reactor internally equipped with a series of alternating counter-pitch spirals and plates.

Such a reactor was developed by Armenja
No. 3,286,992, issued November 22, 1966, filed by Des et al. Well, the characteristics of a tubular reactor with a suitable cutting board are
A comparison is made to a tubular reactor without baffles in which the same graft material flows at the same initial temperature. A comparison of heat transfer in chemical reactors is based on the well-known dimensionless engineering parameter NusseIt number (N
u).

If h is the film coefficient of heat transfer, D is the characteristic dimension of the reactor (for example, the inner diameter), and k is the thermal conductivity of the fluid, then in the comparison of the tubular reactor with and without the baffle plate, D and k is the same, but a suitable tubular reactor with a diagonal plate is at least 2 to 2112 of a tubular reactor without a diagonal plate.
times the Nutsselt number, thus indicating heat transfer.

Another indication of the integrity of mixing in the baffled reactor used in the process of the invention is a comparison of the radial temperature gradient in the heated section of the reactor.

A tubular reactor without a jamb plate exhibits a temperature difference (radial temperature gradient) of around 60° C. between the heated boundary layer of 350° C. and the center of the reactor. In contrast, a suitable plated reactor exhibits only a radial temperature gradient of about 6-9°C, in any case less than 10°C. A suitable baffled tubular reactor exhibits a radial temperature gradient that, under the same conditions, is less than about 15 cents of the gradient in a reactor without baffles. The degree of axial mixing or dispersion in a suitable tubular reactor is
can be evaluated by a dimensionless engineering parameter known as the clet number (Pe).

v is the average linear flow velocity in the reactor, L is the characteristic length of the reactor, E
is the dispersion coefficient measured in the axial direction, then in a tubular reactor suitable for the present invention, the flow of material can be described as a single dispersion plug flow. A dispersed plug flow means a plug flow in which a certain degree of axial dispersion (backmixing) is superimposed at the front end of the flow. Such dispersive plug flow means that each element of material is retained in the reactor for substantially the same amount of time, and that the other material in a region of the material is concentrated in the radial direction, rather than in the axial or longitudinal direction. gives the result that there is more movement (i.e. mixing of materials) for the area. When the system exhibits dispersed plug flow, the axial dispersion coefficient E
is extremely small. Ideal distributed plug flow gives E equal to Z and infinite Becclet number. In systems with high axial dispersion (backmixing) and little radial mixing, E is very large. Ideal backmixing gives E equal to infinity and a vector number of zero. For practical purposes, a Becklet number of 100 is said to confirm distributed plug flow;
and a tubular reactor with a suitable uniform plate is at least 10
Indicates the vectorette number of 0. In general, tubular reactors with Becclet numbers of at least 100 exhibit the necessary low radial temperature gradients, have dispersed plug flow, and are preferred reactors. In addition to the above-mentioned U.S. Pat. No. 3,286,992, reactors exhibiting the above-mentioned distributed plug flow characteristics are
For example, Chemical Engineering Progress, Vol. 71, No. 1 (January 197), pp. 54-58 and KTEK-12345678 (Radial Mixing and Residence●Time distribution●In the●Static●Mixer unit)
It is also known and described in the literature, and various products are commercially available.

In practicing the invention, the reaction components are mixed and rapidly heated to a uniform reaction temperature.

After the grafting reaction, the temperature is lowered rapidly and uniformly. In principle, all stages of heating and cooling must be carried out quickly, but there are some stages where chemical reactions can occur that are considered to be critical. Heating of the reaction components from about 300° C. to the grafting temperature should be accomplished in less than 2 minutes, preferably less than 1 minute, and from the grafting temperature of the grafted polymeric material to about 300° C.
Cooling to °C should be achieved in less than 3 minutes, preferably less than 1 minute. The rate of temperature change for the heating and cooling stages is at least 1 per second.
℃, preferably 2℃. The reaction components are intimately mixed so that each element of the material experiences substantially the same reaction temperature for substantially the same amount of time. The duration of the reaction is generally less than about 1 minute and greater than about 114 minutes. Most preferred durations are from about 5 minutes to about 112 minutes, although relatively short maximum times are important to avoid excessive decomposition, crosslinking and other undesirable side reactions. A suitable range of grafting reaction temperature is about 275 to about 55
0°C, preferably about 350 to about 500°C.

Tight temperature control, small radial temperature gradients and uniform short residence times allow the use of high grafting temperatures without the excessive stem degradation and crosslinking that would be expected at high temperatures. For the first class of substantially saturated backbone polymers that require thermal racking for the grafting reaction, the process of the present invention can be applied to
It is carried out at 0°C, preferably about 400-500°C.
For the second class of backbone polymers having side chain unsaturation, grafting according to the invention is carried out at about 275-450°C, preferably about 350-450°C. Generally, the method of the invention comprises mixing a backbone polymer and a graft monomer,
and subsequent introduction of the mixture into a tubular reactor exhibiting dispersive plug flow. The mixture is rapidly heated to the reaction temperature and the now molten mixture is introduced into the reactor to effect the grafting reaction. After the grafting reaction is complete, the grafted polymeric material is rapidly cooled to a temperature below about 300°C. It should be understood that the process of the present invention contemplates the introduction of an already heated mixture of backbone polymer and graft monomer into the reactor. The order of heating the materials and their introduction into the reactor can be alternated within the scope of the invention. Approximately 0.01 to approximately 201
Preferably about 0.1 to about 101, preferably about 0
．． It is generally desirable or necessary to produce a graft polymeric material having from 2 to about 5 weight percent graft monomer.

An excess of grafting monomer in the reaction mixture and a backbone polymer having a degree of unsaturation in excess of that necessary for the desired degree of grafting are useful. As a general rule, and assuming excessive unsaturation, 50 percent, and in some cases more, of the graft monomer can be effectively grafted onto the backbone polymer. The grafting reaction of the process of the invention is carried out without the use of promoters, catalysts or other free radical generating additives.

Therefore, the amount of decomposed backbone polymer produced is small.
The method of the present invention, with uniform temperatures, uniform residence times, and rapid temperature changes, allows grafting reactions to be accomplished without the need for free radical generating additives. Thus, polymer degradation is reduced both by eliminating non-uniform temperature conditions and by eliminating chain-severing additives. In the following examples, the backbone polymer and graft monomer are:
The mixture is mixed before introduction into the reactor with baffles and the mixture is fed into the reactor by the force provided by the screw extruder. As an example of a suitable tubular reactor with an internal baffle plate to provide dispersion plug flow and other necessary parameters, the reactor often used in the following examples is approximately 3.8 Crfi (1
Static mixer (112 inches) and commercially available from Kenix Corporation, Denver, Mass., USA.
Product name). The reactor described herein need not encompass the entire length of the vessel with internal baffles. The plated tube section of the reactor is the section that is maintained at a temperature suitable to accomplish at least about 80% of the total grafting reaction. Percentages are by weight unless otherwise indicated. ．． The reactor is a closed system and all grafting reactions are carried out without the presence of free radical generating additives. Melt indexes noted herein generally refer to ASTM
(D-1238-70).

In this test, a diameter of 0.0825 inches (a).
210 cm), length 0.315 inch (4). 800α
) is the weight (
grams) to 0.373 for the material at a temperature of 190°C.
Inch (a). 947 cm) and a total weight of 2.160 grams. Example 1 In this example, fumaric acid is the graft monomer and linear high density polyethylene homopolymer (a). 95
8y/Cm) is the backbone polymer.

The backbone polymer has a melt index of about 3. Cuboidal backbone polymer and graft monomer particles are mixed and introduced into a reactor at a temperature of about 330°C.

The graft monomer in the mixture is about 2 percent. Raise the temperature to about 420℃ in about 1 minute, and reduce this temperature to about 2.5℃.
during which time the reaction mixture reaches approximately 45 cm in the reactor.
Move forward (approximately 1.5 feet). The total length of the reaction tube is approximately 75
cm, and the total residence time in the reactor is approximately 4 minutes. The grafted polymeric material is then cooled to below about 270°C and discharged from the reactor. The melt index of the grafted polymer material is about 10-20, and the degree of grafting is about 0.
．． It is recognized that the percentage is 6%.

The pressure drop in the reactor is approximately 7k9/CTi (100
bond/parallel inch). Substantially the same results occur if other suitable grafting monomers are used in place of fumaric acid in this example, such as maleic anhydride.

Other polyethylene backbone polymers can also be used in place of the polyethylene in this example. Alternatively, the mixture of backbone polymer and graft monomer may be heated to reaction temperature prior to introduction into the reactor. Example 2 In this example, the graft monomer is monoethyl ester of maleic anhydride (MAME) and the backbone polymer is a copolymer of ethylene, propylene, and 1,4-hexadiene.

The backbone polymer is a material consisting primarily of a saturated backbone and unsaturated side chains, with about 71 percent ethylene and about 25 percent ethylene.
/cents of propylene and about 4 percent diene. This backbone polymer exhibits a melt index of about 0.1 using a melt index test temperature of 280°C. The cubic backbone polymer and about 1 percent of the graft monomer are mixed prior to introduction into the reactor.

As in the previous example, the reaction is heated to about 350°C.
This temperature is approximately 5.7-6. After stirring to complete the grafting, the grafted polymer material is cooled to below 300° C. and discharged from the reactor. When the reaction temperature is low, the residence time must be increased to obtain the desired result.
It must be raised accordingly. Relatively high reaction temperatures allow relatively short residence times. Substantially the same results occur when using other backbone polymers with unsaturated side chains.

Other backbone polymers and, for example, each about 70/2
Mention may be made of copolymers derived from ethylene, propylene, 1,4-hexadiene and norbornadiene in a weight ratio of 3/6.75/0.25. Instead of monoethyl ester of maleic anhydride in this example,
Other graft monomers can also be used. Fumaric acid, maleic acid, maleic anhydride, methacrylic acid, glycidyl methacrylate, etc. can all be expected to give similar results. Of course, different concentrations of graft monomer will provide graft polymer materials with different graft contents. Example 3 This example provides an indication that short residence times, rapid mixing and temperature changes are desirable with respect to decomposition of the backbone polymer during the grafting reaction.

The backbone polymer and graft monomers are similar to those used in Example 2, and the reactor and procedure are as in Example 1.

Three graft reactions are carried out, each at a different flow rate in the reactor, with other conditions being the same. The amount of maleic anhydride ethyl ester used is 1-2 percent and the reaction temperature is 380-385C.

Melt index test temperature is 280°C. The graft polymeric material is prepared as follows: Example 4 This example shows that the backbone polymer of Example 2 and fumaric acid were uniformly mixed at a fumaric acid content of 3 percent, each in pellet or powder form. Using acid grafting monomers.

The reaction temperature is 365-370°C and the reaction duration is about 3.1-3.4 minutes.

The graft polymeric material has an acid anhydride content of approximately 1
．． It is found to contain between 5 and 1.6 cents of fumaric acid.

The melt index of the grafted monomer material is approximately 3 using a test temperature of 280°C. Substantially the same results are achieved when any of the above examples are repeated using a larger size or higher capacity reactor with a suitably side plate.

For example, repeating the reaction of Example 4 using a suitable reactor with an internal diameter of about 5 cwt gives the following results: (
1) a mixture containing about 4 percent fumaric acid content;
Using a temperature of about 400°C and a reaction time of about 3.5-4.5 minutes, about 1.75 percent grafting
A melt index of 5 is achieved (measured at 280°C); (2) a fumaric acid content of about 8 percent;
Using a temperature of about 365-370°C and a reaction time of about 8-8.5 minutes, about 3.5 percent grafting was achieved at a Melton Index of about 15.6 (measured at 280°C). be done. Example 5 This example illustrates variations in the combination of reaction components and introduction of the components into the reaction conditions.

The graft monomer is fumaric acid and the backbone polymer is high density polyethylene with a melt index of about 3.
After melt-mixing the polyethylene backbone polymer and about 4% fumaric acid at a temperature below the grafting reaction temperature, the molten mixture is
Mix with additional polyethylene backbone polymer on the same weight basis. The resulting molten mixture is 5C77! having an inner diameter of
It is introduced into a reactor similar to the one used earlier. The reaction temperature is about 400-440°C and the reaction time is about 5.2 minutes. Approximately 0.9% grafting is observed in the grafted polymer material and the melt index is approximately 15.5. The graft polymeric materials of the present invention can be used alone or in combination with other polymeric materials to
They find important use as elastomeric materials for the construction of components, such as gears or bushings, with specific sliding or friction properties.

Claims (1)

[Scope of Claims] 1. (a) mixing an ethylene-based backbone polymer and a graft monomer, and (b) introducing the mixture into a tubular reactor exhibiting dispersion plug flow characteristics, provided that the tubular reactor is A series of alternating counter-pitch spiral chopping plates is provided internally to ensure that the mixture is mixed more radially than in the axial direction of the tubular reactor and that each portion of the mixture is substantially contained within the tubular reactor. (c) Raising the temperature of the mixture to 275-550°C (d)
introducing the mixture into a tubular reactor for a time adequate to accomplish the grafting reaction but too short to cause excessive decomposition, maintaining the temperature of step (c) for 10 to 1/4 minutes; A method for producing a graft polymer material by bulk polymerization without the use of free radical-generating additives, characterized in that the graft polymer material is produced. 2. The method of claim 1, wherein the temperature of the graft polymer material is reduced from the temperature of step (c) to a temperature below 300° C. in less than 3 minutes. 3. The method of claim 1, wherein the temperature of step (c) is maintained for less than about 5 minutes. 4. The method of claim 1, wherein the backbone polymer is selected from the group consisting of thermoplastic and elastomeric polymers of ethylene and copolymers derived from ethylene and C_3 to C_8 alpha-olefins. 5. The method of claim 4, wherein the backbone polymer is substantially saturated. 6. The method according to claim 5, wherein the backbone polymer is high density polyethylene. 7. The method of claim 4, wherein the backbone polymer has a substantially saturated backbone chain and unsaturated side chains. 8 The backbone polymer is ethylene and at least one type of C_3-C
8. The method of claim 7, wherein the copolymer is a copolymer of 8 alpha-olefins. 9. The method according to claim 8, wherein the backbone polymer is a copolymer of ethylene, propylene, 1,4-hexadiene and norbornadiene. 10 The reaction was carried out for about 10 to 1/4 min at a temperature of 275 to 550 °C in a tubular reactor exhibiting dispersive plug flow characteristics, a radial temperature difference of less than 10 °C, and a Peclet number of greater than 100. A method according to claim 1, which is carried out over a period of time. 11. The method of claim 10, wherein the reaction temperature is from 350 to 500C and the duration of the reaction is from about 0.5 minutes to about 5 minutes.